Yes, "that song," the one that won't leave the radio dial or the inner reaches of your brain -- Cee-Lo, Dangermouse, pop music gold, baby!
Thank god for the Internet -- some blogging crate digger has unearthed the sample behind "Crazy," and it's pretty damn obscure. From the 1968 spaghetti Western ""Preparati la bara" or "Django, Prepare a Coffin," the song is called "Last Man Standing" ("Nel Cimitero Di Tucson"). The bass line, choral voices and spooky atmosphere can clearly be heard.
Take a listen